CONCORD — Lennar Urban will get the first shot at transforming the Concord Naval Weapons Station into a thriving community with housing, parks, retail and office space.

During a special meeting Wednesday, the City Council voted unanimously to select Lennar as master developer of the first phase of the multimillion dollar project which includes approximately 500 acres of the former military base.

“I think this is a great deal, I think it’s beneficial to all concerned and I think it’s a fair deal,” Councilman Edi Birsan said.

The next steps include negotiating the formal contract, known as a disposition and development agreement, which could take six to nine months. Lennar has agreed to initiate and pay for the land use plan and environmental work while the two parties hammer out the contract.

“We are very grateful for this opportunity. It’s been a long road to get here,” Lennar regional Vice President Kofi Bonner said in a written statement. “There is a lot of work ahead of us, but I can assure you that we are committed to working with city staff, the U.S. Navy and the people of Concord to remake the Naval Weapons Station into a vibrant new area that will make this city proud.”

Lennar revised its financial proposal to commit $40 million for affordable housing and to spend nearly $16 million to widen Willow Pass Road to four lanes and rebuild Willow Pass bridge as a four-lane span.

But the company also reduced by $10 million the guaranteed payout Concord would receive to $20 million over 10 years. Once Lennar earns a 20 percent return on its investment, it will share the profits which could amount to an additional $23 million for the city.

The Concord Reuse Project Area Plan calls for building up to 12,272 housing units and 6.1 million square feet of commercial space on about 2,300 acres of the former military base. The Navy is scheduled to begin transferring land to the city in the spring of 2017.

Concord was forced to delay the decision for months to look into allegations from Catellus Development Corp., a former competitor for the contract, that Lennar had engaged in improper lobbying. An independent investigator concluded that Lennar had orchestrated donations to former Mayor Tim Grayson’s Assembly campaign.

“Given a project of this magnitude, it’s to be expected that mistakes would be made and they were,” Councilman Dan Helix said. “The train went off the tracks.”

But he lauded city staffers for working diligently with Lennar to improve its offer, particularly with respect to providing funds for affordable housing and bonds that guarantee that the infrastructure is built.

Rather than transfer the entire 500 acres of the first phase to Lennar at one time, the city will turn over individual parcels when Lennar is ready to begin development, and the company demonstrates that it has the funds to do the work, posts bonds and secures insurance.

Still, a few detractors urged the council to reject Lennar and begin a new search for a master developer.

“I still don’t feel comfortable with Lennar,” said Ralph Oliver, a 24-year Concord resident who lives in the Sun Terrace neighborhood. “The more I learn about Lennar, the more I feel they will act unethically when it suits them.”